Chemicals of Emerging Concern (CECs) identified in sewage sludge

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Thousands of chemicals serving a variety of human needs flood into sewage treatment plants once their use life has ended. Many belong to a class of chemicals known as CECs (for chemicals of emerging concern), which may pose risks to both human and environmental health. Arjun Venkatesan and Rolf Halden of Arizona State University's Biodesign Institute have been tracking many of these chemicals outlining a new approach to the identification of potentially harmful, mass-produced chemicals, describing the accumulation in sludge of 123 distinct CECs.

Thousands of chemicals serving a variety of human needs flood into
sewage treatment plants once their use life has ended. Many belong to a class
of chemicals known as CECs (for chemicals of emerging concern), which may pose
risks to both human and environmental health.

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Arjun Venkatesan and Rolf Halden of Arizona State University's
Biodesign Institute have been tracking many of these chemicals outlining a new
approach to the identification of potentially harmful, mass-produced chemicals,
describing the accumulation in sludge of 123 distinct CECs.

Ten of the 11 chemicals found in greatest abundance in treated
municipal sludge or biosolids were high-production volume chemicals, including
flame-retardants, antimicrobials and surfactants.

The study shows a strong overlap between chemicals found in biological
samples taken from the human population and those detected in municipal
biosolids. These findings suggest that analysis of sludge may provide a useful
surrogate for the assessment of human exposure and bioaccumulation of
potentially hazardous substances.

According to Venkatesan, "presence of CECs in sewage suggests
that consumers already may get exposed to these chemicals prior to their
discharge into sewage, suggesting a need for human biomonitoring and risk
assessment of these priority chemicals."

Prioritizing
the thousands of CECs and predicting their behavior has been a daunting challenge.
Evaluation is costly, tedious and time-consuming. Further, as the new study
emphasizes, laboratory modeling of chemical behavior, including rates of
environmental breakdown and potential for bioaccumulation often deviate
significantly from real-world scenarios.

Conventional chemical screening evaluates the persistence,
bioaccumulation and potential toxicity of various chemicals. The method however
suffers from two shortcomings: the production rates of chemicals in current use
are not incorporated into analysis and the detailed behavior of these chemicals
in real-world biological systemsâ€”including the human bodyâ€”is not assessed.

In the current study, a repository of samples from U.S. wastewater
treatment plants, created and maintained by the team was used to conveniently
identify CECs, as well as evaluate their potential for bioaccumulation and
their ability to withstand degradation processes. The working hypothesis
proposes that such treatment plants may act as reliable gauges for monitoring
chemical prevalence and bioaccumulation potential relevant to human society and
the environment.

Specifically, chemicals managing to survive primary and secondary
treatment in municipal sewage systems display notable resistance to aerobic and
anaerobic digestion processes and are therefore more likely to stubbornly
persist in the environment upon their release.